FIG. 12 is a perspective view that shows an example of an existing tuning bar vibrator. The tuning bar vibrator 1 includes two rectangular piezoelectric substrates 2a and 2b. These piezoelectric substrates 2a and 2b are laminated via an electrode 3. These piezoelectric substrates 2a and 2b are polarized in opposite directions to each other as shown by the arrows in FIG. 12. Two split electrodes 4 are formed on the principal surface of the piezoelectric substrate 2a. These split electrodes 4 are separated at the center of the piezoelectric substrate 2a in the width direction, and is formed so as to extend in the longitudinal direction of the piezoelectric substrate 2a. In addition, a common electrode 5 is formed on the entire area of the principal surface of the other piezoelectric substrate 2b. The tuning bar vibrator 1 connects an oscillation circuit between the split electrodes 4 and the common electrode 5, so it bends and vibrates in a direction perpendicular to the principal surfaces of the piezoelectric substrates 2a and 2b. Support members 6 are formed at nodes of the bending vibration.
The tuning bar vibrator 1 is, for example, used as a vibrating gyroscope. In this case, an oscillation circuit is connected between the split electrodes 4 and the common electrode 5. In addition, the split electrodes are connected to a differential circuit, and a difference in output signal between the split electrodes 4 is detected. Owing to a driving signal of the oscillation circuit, the tuning bar vibrator 1 bends and vibrates in the direction perpendicular to the principal surface of the piezoelectric substrates 2a and 2b. Here, the tuning bar vibrator 1 is bent and vibrated by self-oscillation that vibrates at its resonant frequency. In this state, when an rotational angular velocity is applied about the central axis of the tuning bar vibrator 1, Coriolis force acts in a direction perpendicular to the direction of bending vibration at the time when the tuning bar vibrator 1 is not rotated. Thus, the direction of bending vibration of the tuning bar vibrator 1 changes, signals in opposite phase, corresponding to Coriolis force are output from the two split electrodes 4, and then a difference in these signals is output from the differential circuit. Thus, by measuring the output signal of the differential circuit, it is possible to detect a rotational angular velocity applied to the tuning bar vibrator 1 (see Patent Document 1).    Patent Document 1: Japanese Unexamined Patent Application Publication No. 7-332988